Hibernation Records on the Surface of Rodent Incisors: Intraspecific Variations and Interspecific Differences

Biology Bulletin - This paper discusses intraspecific variations and interspecific differences in the “hibernation zone” and the mechanism of its formation on the incisor surface in...     

First Data on Non-occlusal Surface Incisor Microwear of Cave Bears from the Urals

Doklady Biological Sciences - The microwear of the non-occlusal surface of incisors (I1, I2) of the small cave bear (Ursus ex gr. savini-rossicus) and Ural cave bear (Ursus kanivetz) from the...     

Interspecific Variations in Responses of Mangrove Seedlings to Two Contrasting Salinities

The growth performance of seedlings of seven species of true mangroves (Avicennia marina, A. officinalis, Bruguiera gymnorrhiza, B. sexangula, Rhizophora apiculata, R. mucronata, and Sonneratia caseolaris) in response to two contrasting salinity regimes, low (i.e., 3–5) and medium (i.e., 25–27), was studied. Species represented all categories relevant to vivipary (i.e., true viviparous species, cryptoviviparous species and non‐viviparous species), and included closely related pairs as well as species commonly used in replanting in Sri Lanka. Species could be ranked in descending order of salinity tolerance as A. marina > R. mucronata > R. apiculata >B. gymnorrhiza > A. officinalis > B. sexangula > S. caseolaris, hence taxonomically similar species and those sharing vivipary characteristics may be distant in salinity tolerance. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Daily Variations in the Sensitivity of Soybean Seedlings to Low Temperature

Every 4 hr during a time span of 32 hr and of 76 hr a different group of soybean seedlings [Glycine max (L.) Merr., cv. Corsoy] maintained under a regime of 16 hr of light followed by 8 hr of darkness was exposed to -10°C for 4 min. Extent of sensitivity to low temperature was evaluated approximately 10 days alter exposure to freezing temperature by determining the weight of the plants and chlorophyll content of the cotyledons. The amount of sensitivity to low temperature was related to the time of exposure and displayed a significant 24-hr oscillation. Plants appeared to be least sensitive to cold injury during the late portions of the light span. Plants subjected to water stress were less sensitive to cold and no significant 24-hr oscillation in response to low temperature could be detected by the cosinor method of analysis.     

Daily Variations in the Responses to Papaverine but not Theophylline in Rat Aorta

The presence of temporal patterns in the responses of vascular smooth muscle to relaxing agents have been known. The aim of this study was to examine the variations in the in vitro sensitivity of rat aorta to papaverine and theophylline in both endothelium-intact and -denuded rings. The animals were synchronized with a 12-h light: 12-h dark schedule. Rat thoracic aorta rings were obtained from animals sacrificed at six different times (09:00, 13:00, 17:00, 21:00, 01:00 and 05:00) of the day. Tissues were precontracted submaximally with phenylephrine and then were relaxed by papaverine (10^?8 ? 10^?4 M) and theophylline (10^?7 ? 10^?3 M) applied cumulatively. The responses to most of the concentrations and EC₅₀ values for papaverine demonstrated an ultradian rhythm with an 8 h periodicity. Time-dependent variations were not found in the responses to theophylline. The results are discussed in relation with the time-dependent differences in signal transducing mechanisms.     

Daily Variations in the Responses to Papaverine but not Theophylline in Rat Aorta

The presence of temporal patterns in the responses of vascular smooth muscle to relaxing agents have been known. The aim of this study was to examine the variations in the in vitro sensitivity of rat aorta to papaverine and theophylline in both endothelium-intact and -denuded rings. The animals were synchronized with a 12-h light: 12-h dark schedule. Rat thoracic aorta rings were obtained from animals sacrificed at six different times (09:00, 13:00, 17:00, 21:00, 01:00 and 05:00) of the day. Tissues were precontracted submaximally with phenylephrine and then were relaxed by papaverine (10^-8 - 10^-4 M) and theophylline (10^-7 &miknus; 10^-3 M) applied cumulatively. The responses to most of the concentrations and EC₅₀ values for papaverine demonstrated an ultradian rhythm with an 8 h periodicity. Time-dependent variations were not found in the responses to theophylline. The results are discussed in relation with the time-dependent differences in signal transducing mechanisms.     

Interspecific fusion of sea urchin eggs: Surface events and cytoplasmic mixing

Here we describe a new method of fusing fertilized and unfertilized sea urchin eggs. After removal of materials peripheral to the plasma membranes, the plycation polyarginine is used to induce the eggs to adhere to one another. The subsequent incubation of the eggs in an artificial sea water with a slightly lower osmolarity and a higher calcium content than normal sea water results in successful fusion. We demonstrate with scanning electron microscopy (SEM) that our artificial sea water serves to smooth the plasma membranes—a characteristic which we find to be a requirement in order for fusion to occur. We also demonstrate that our fusion procedure can be used to identify and follow the development of hybrids composed of eggs of different histories. Using species whose cytoplasms are distinguishable by light microscopy, Strongylocentrotus purpuratus and Lytechlnus pictus, we consider the mixing of cytoplasms using yolk granules as markers. We find that if two unfertilized eggs are fused, the species-specific yolk particles are free to mix. In contrast, we observe no mixing of the yolk particles in either fertilized-unfertilized or fertilized-fertilized interspecies hybrids until the time of mitosis. At that time, the yolk particles are free to move around the region containing the mitotic figure(s). However, mixing of the cytoplasmic yolk granules is never completed during this brief period. Even after cytokinesis takes place, one can see the segregation of the yolk granules in the cytoplasms of the two species.     

Further Study on the Esterase Patterns of Sibling Species in the Drosophila saltans Subgroup (saltans Group): Intraspecific and Interspecific Variations in the Development

Twenty of the 32 esterase bands previously detected in the adults of D. prosaltans, D. saltans and D.␣austrosaltans were found in larvae and pupae studied in this work. The results showed that, in addition to expressing the highest number of esterase bands, the adult stage of the three species exhibited the highest degree of expression (amount of synthesis) for most of the bands. Differences between larval and pupal stages were detected in the degree of expression (amount of synthesis) of the bands and in the frequency of samples expressing them. The frequencies of expression of the bands corresponding to genes in loci 1–3 were greater in pupae than in larvae while the frequencies of expression of the bands corresponding to genes in loci 4–9 were predominantly expressed in larvae or were equal in both developmental stages. Like the adults, larvae, pupae and empty pupal cases (which were also studied in this work) showed specific esterases. Taken together, the observations showed that, in the species studied, every developmental stage is characterized by specific bands and by specific frequency and degree of expression of the bands shared with other stages.     

Daily Variations of Functional Parameters and Density Distribution in Human Blood Platelets

Blood platelets play a critical role in the onset of myocardial infarction, which has been shown to have a circadian rhythmicity with a peak incidence in the morning. In an attempt to correlate platelet parameters with the outcome of cardiovascular diseases, we studied the daily (24-h) variation of the following platelet parameters: distribution pattern of functional heterogeneous platelet subpopulations; serotonin uptake; ketanserin binding; aggregation upon thrombin, serotonin, and ADP stimulation; and platelet count. Furthermore, we analyzed the tryptophan and serotonin concentrations in the blood samples. The percentage of less dense platelets, which represent the subpopulation with the highest preactivation, showed a rhythmicity period of 24 h and an acrophase at 21:18 h. The time course of intermediate and high density platelets was inverse to that of low density platelets. The serotonin uptake exhibited also a rhythmicity with a 24-h period. The acrophase was at 13:50 h. The aggregation curves were inverse to the ketanserin binding curves. The serotonin concentration exhibited a 12-h rhythmicity. The results obtained suggest that (a) changes in platelet activity are reflected by several parameters of platelet function that underlie daily variations; (b) the aggregation curves show a peak in the morning, with an additional peak in the afternoon; and (c) changes in the distribution pattern occur independently from variations in platelet functions like aggregation and serotonin binding.     

穴居啮齿动物震动信号的意义及研究展望

穴居啮齿动物一般生活在黑暗、复杂的地下洞道环境中。营地下生活的特殊栖息环境使其进化出了与环境相适应的震动通讯,用来实现个体或社群间的信息联系。震动通讯是动物界中一种独特的信息传递方式,穴居啮齿动物的震动通讯已成为行为生态学研究的热点之一。了解震动信号发生和接收的部位、特征及其生物学意义,对于完善和发展穴居啮齿动物基础研究具有重大意义。但是,对于穴居啮齿动物来说,其独特的地下栖息生活方式增加了解读震动信号的难度。这些挑战导致穴居啮齿动物震动通讯方面研究进展缓慢、科研文章较少。本文在查阅国内外穴居啮齿动物震动通讯研究文献的基础上,分别从具有震动通讯特征的穴居啮齿动物种类、分布,震动信号发生和接收部位,震动信号的作用以及研究方法等方面进行了概述,并展望了震动信号在鼠害防控、医疗等领域应用的可能性。本文旨在为今后研究穴居啮齿动物震动通讯提供参考。     

Daily Variations of Homocysteine Concentration May Influence Methylation of DNA in Normal Healthy Individuals

The regulation of genetic expression is tightly controlled and well balanced in the organism by different epigenetic mechanisms such as DNA methylation and histone modifications. DNA methylation occurring after embryogenesis is seen mainly as an irreversible event. Even small changes in genomic DNA methylation might be of biological relevance, and several factors influencing DNA methylation have been identified so far, one being homocysteine. In this study, genomic DNA methylation was analyzed and homocysteine plasma levels were measured over a 24 h period in 30 healthy students (15 males and 15 females) exposed to a standard 24 h regime of daytime activity alternating with nighttime sleep. Plasma homocysteine concentrations were measured using HPLC detection. DNA was extracted from whole EDTA blood, and genomic DNA methylation was assessed by fluorescently labeled cytosine extension assay. Both homocysteine and DNA methylation showed 24 h variation. Homocysteine showed a significant daily rhythm with an evening peak and nocturnal nadir in all subjects (p<0.001). Males showed higher overall homocysteine levels compared to females (p=0.002). Genomic DNA methylation showed a significant rhythm with increased levels at night (p=0.021), which was inverse to plasma homocysteine levels.     

Intra-and interchromosomal effects of heterozygous inversions on recombination in the third chromosome of Drosophila ananassae

In order to study intra-and interchromosomal effects of heterozygous inversions on recombination in the third chromosome of D.ananassae, experiments were conducted using Stw-pr marker stock and five wild stocks with known karyotypes. The stocks used were homozygous for standard or inverted gene sequence in 2L, 3L, and 3R. Recombination was investigated in both sexes. There was complete absence of crossing-over in males in all the experiments which appeared to be the characteristic of marker stock as spontaneous male crossing-over was reported earlier with the same wild stocks when the second chromosome markers were used. Based on the data of karyotypically homozygous F1 females, the map distance between stw-pr was 36.55 map units. The heterozygosity due to a lengthy inversion in 2L increased the level of crossing-over between stw-pr genes of the third chromosome indicating interchromosomal effect. There was a considerable reduction in the rate of recombination between the same markers due to inversion heterozygosity in 3R indicating intrachromosomal effect. However, 3L inversion heterozygosity had no effect on crossover rate. These results provide evidence for intra-and interchromosomal effects of inversions on crossing-over in the third chromosome of D. ananassae.     

Effect of Pineal Extirpation on Daily and Long-Term Variations in Thermal Tolerance in a Tropical Catfish,Clarias batrachus

Thermal tolerance in laboratory acclimated Clarias batrachus was assessed by determining the critical thermal maximum (CTM) every 4 hours for 2 days in intact and pinealectomized (Px) animals during January and in sham-pinealectomized (sham-Px) and Px animals during April. In the intact and sham-Px group a statistically significant (P &lt;0.005) diurnal cycle of thermal tolerance was validated which was asynchronous with that of the daily fluctuations in ambient temperature (Ta). A nocturnal elevation of thermal tolerance was observed in all the groups. Pineal removal resulted in a highly significant (P &lt;0.001) increase of CTM. Additionally, pinealectomy abolished the normal diurnal cycle in CTM or dampened its amplitude considerably. In another experiment the long-term effect of pinealectomy on thermal tolerance was determined in sham-Px and Px fishes. CTM was significantly (P &lt;0.05) elevated during the first three weeks following pinealectomy, pointing to a short-term control from the pineal on thermal tolerance. This study provides the first demonstration of a direct pineal influence on thermal tolerance and its temporal organization.     

Ultrastructural Observations on the Distribution of the Intra-and Intercellular Cytoskeleton of the Endosperm Cells in Triticum aestivum

By means of Triton X-l00 extraction and DGD (diethylene glycol distearate) embedment-free section method the distribution pattern and characteristics of intra- and intercellular cytoskeleton of endosperm cells of Triticum aestivum L. were studied with electron microscopy. Threedimensional architecture of the cytoskeleton could be recognized as a meshwork mainly composed of microtubules (MT) and microfilaments (MF). Attention was stressed on the interface of the adjoining cytoskeletal frameworks where an attractive phenomenon observed was that the MF extruding from the surface of the cytoskeleton often traversed the whole wall boundary and connected the neighbouring frameworks into an entity. In the endosperm tissue two types of transcellular MF distribution could be distinguished, the MF in bundles traversing the enlarged intercellular channels and the MF individually penetrating the wall boundary; that seemed to coordinate with the co-presence of normal and modified plasmodesmata in the same wall. The above observations demonstrated the intercellular cytoskeletal continuity within the symplast and confirmed that the MF was the main constituent of the traversing cytoplasmic strands, the possibility of MF being organized as a structural element of the normal plasmodesmata was also discussed.     

啮齿动物的嗅觉通讯研究进展

通过对近40 年来啮齿动物嗅觉通讯的研究综述, 主要介绍嗅觉信号的来源、组成及其对啮齿动物行为生理所产生的作用。啮齿动物嗅觉通讯的信号来源主要是粪便、尿液和特化皮肤腺等, 对这些化学信号的成分分析主要集中在各种信息素(Pheromone) 的结构、来源及其引起的行为反应。目前, 在对啮齿动物嗅觉通讯神经通路的研究中, 对主嗅觉系统和犁鼻器系统在动物嗅觉通讯中的作用仍将是人们研究的重点; 而通过信息素作用所产生的各种行为反应的神经内分泌机制也是动物嗅觉通讯领域研究的热点之一。研究气味信号对动物行为和生理等方面所产生的作用, 将有助于揭示啮齿动物嗅觉通讯在其社会行为中的重要作用。     

Intra-and intercolony patterns of nest dispersion in the ant Lasius neoniger: correlations with territoriality and foraging ecology

Colonies of the ant Lasius neoniger have multiple nest entrances that are distributed throughout a colony's foraging area. Associated with each nest entrance is a group of workers that show strong fidelity to that nest entrance. Territorial expansion, as indicated by increases in the number of nest entrances per colony, is correlated with foraging activity. Although there is variation between colonies in the seasonal pattern of territorial expansion, most nests become active in early summer, increase the size of the area foraged until midsummer, and then decrease the number of active nest entrances in late summer. Over the study plot as a whole, the dispersion pattern of nest entrances changed from clumped, or tending to be clumped, in early spring to random in mid-and late summer. Within colonies, nest entrances were significantly overdispersed. Intra-and interspecific competition negatively affected foraging, and workers from a given nest entrance were most successful at retrieving prey less than approximately 15–20 cm from the entrance. The average distance between nest entrances within a colony was 37.7±3.3 cm (mean±95% confidence interval, n=115), which is approximately twice the distance at which workers can retrieve prey. The polydomous nest structure of L. neoniger appears to partition territory within a colony by spatial subdivision of its foragers, and thus may reduce loss of prey to competitors.